Dental prophylaxis instrument

ABSTRACT

A dental handpiece for cleaning teeth by means of cleaning paste carried by a flexible cup to which rotary motion is imparted by structure entirely within the handpiece. In the disclosed embodiment, a small rotor is powered by the available compressed air supply and the cup is secured to the rotor for rotation thereby. Reciprocal rotary motion is preferably imparted to the cup, again by structure entirely within the handpiece. Several embodiments of detachable cups are disclosed, all of which may be removed and replaced without handling the rotor, and mechanism may also be provided for feeding the cleaning paste directly from a dispenser into the cup from the inside. The actuating member controlling on-off operation is also conveniently located on the handpiece.

United States Patent 1 Graceffo [451 July 30, 1974 DENTAL PROPHYLAXISINSTRUMENT [22] Filed: Apr. 17, 1972 [21] Appl. No.: 244,546

[52] US. Cl. 32/58, 32/59 [51] Int. Cl. A61C 3/06 [58] Field of Search32/58, 59, 27, 26

[56] References Cited UNITED STATES PATENTS 1,179,216 4/1916 Ragatz32/59 X 2,135,933 11/1938 Blair 32/27 3,164,903 1/1965 Ellis 32/58 X3,248,792 5/1966 Staunt l 32/26 3,389,468 6/1968 Lewis et al 32/593,407,502 10/1968 Richmond 32/59 3,427,720 2/1969 Berman et a1. 32/27Primary Examiner-Antonio F. Guida Assistant Examiner-J. Q. LeverAttorney, Agent, or Firm-Charles S. Mc Guire 5 7 ABSTRACT A dentalhandpiece for cleaning teeth by means of cleaning paste carried by aflexible cup to which rotary motion is imparted by structure entirelywithin the handpiece. 1n the disclosed embodiment, a small rotor ispowered by the available compressed air supply and the cup is secured tothe rotor for rotation thereby. Reciprocal rotary motion is preferablyimparted to the cup, again by structure entirely within the handpiece.Several embodiments of detachable cups are disclosed, all of which maybe removed and replaced without handling the rotor, and mechanism mayalso be provided for feeding the cleaning paste directly from adispenser into the cup from the inside. The actuating member controllingon-off operation is also conveniently located on the handpiece.

16 Claims, 11 Drawing Figures DENTAL PROPHYLAXIS INSTRUMENT BACKGROUNDOF THE INVENTION This invention relates to instruments for cleaningteeth, and more specifically to a dental prophylaxis handpiece having arotating cup for applying the cleaning paste wherein the mechanism forimparting rotation is contained entirely within the handpiece.

In applicants copending US. Patent application, Ser. No. 21 l,2l6 isdisclosed a dental prophylaxis instru-' ment having, among otheradvantages, a reciprocating rotary motion imparted to the flexible cupby means of which the paste is applied to the teeth. A cord passinglengthwise through the handpiece is looped around a rotor which supportsthe cup. Movement of the cord is cyclically reversed, according to theprior application, by mechanism external to the handpiece to provide thereciprocating rotation to the rotor and cup.

Use of the cord-driven rotor in the manner disclosed in the referencedearlier application provided further advantages over prior devices sinceit eliminated the bevel gears normally used to transmit rotation to thecup. Thus, the frequent necessity of disassembling, cleaning andlubricating the gears was also eliminated. Still further disadvantagesof prior units, e.g., the necessith of operating the on-off and speedcontrols with one foot, and the constant dipping of the cup into adappen dish for fresh paste, were also eliminated by the apparatus ofapplicants earlier application. Details of typical prior art structure,as well as means for overcoming the aforementioned disadvantagesthereof, are discussed at greater length in the earlier application andneed not be repeated here in their entirety. However, it is important tonote that the present invention incorporates the desirable features ofthe earlier application, as well as providing other advantages whichwill be apparent from the ensuing detailed description.

SUMMARY OF THE INVENTION Although the apparatus of the referencedearlier application provides a better polishing action than conventionalprophylaxis instruments wherein cup rotation is in one direction only,the power mechanism for imparting reciprocation is located outside thebody of the instrument, conveyed to the instrument, by means of asleeved cord. A principal advantage to the present invention is theincorporation of a novel reciprocating power mechanism containedentirely within the handle of the handpiece, thus eliminating the needfor an extending cord, or power source outside the handpiece itself.

The dental handpiece of the present invention may be powered by thecompressed air supply normally available for other purposes in thecommon dental operatory. The air supply drives a small, rotary motormember of known design mounted in the handpiece at the opposite end fromthe rotating cup. A cord is connected to transmit motion from theair-driven member to the cup by means of a rotor around which the cordpasses and to which the cup is affixed. Several embodiments of means forreleasably attaching the cup to the rotor are disclosed, therebyallowing the cup to be easily removed and discarded after each usewithout handling the rotor, cord, or other elements. Means may beprovided, and will be described. for supplying the prophylaxis pastefrom a disposable cartridge directly to the cup concavity in anembodiment incorporating the aforementioned removable cup.

The invention further includes embodiments wherein a reciprocatingrotary motion is imparted to the cup by mechanism within the handpiece.According to a preferred construction, the aforementioned air-drivenmember imparts rotation to a shaft extending axially within thehandpiece and having an endless, double helical groove. Reciprocallinear motion is imparted to a follower having a portion extending intothe groove, and thus riding back and forth along the shaft as the latterrotates in one direction. The cord is affixed to the follower and loopedaround the rotor, in the manner previously mentioned, to drive the cup.Thus, rotary movement in one direction is converted to reciprocatinglinear motion, and thence to reciprocating rotary motion, all by meansof structure located within the handpiece. Furthermore, the nature ofthe novel structure is such that the handpiece is not rendered undulylarge or cumbersome by incorporation thereof. A valve controlling airsupply to the rotary member is conveniently movable between open andclosed positions by a button or similar manually engageable member onthe handpiece.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a dentalprophylaxis handpiece embodying the present invention;

FIG. 2 is a side elevational view, partly in section, of the handpieceof FIG. 1;

FIG. 3 is a side elevational view, as in FIG. 2, showing the handpiecein an embodiment which does not incorporate the paste dispensingmechanism;

FIGS. 4, 5 and 6 are enlarged, transverse sectional views takenrespectively on the lines 4-4, 5-5 and 6-6 of FIG. 3, FIG. 6 beingsomewhat diagrammatic;

FIG 4a is an enlarged, plan view of certain elements as seen from theline 4a-4a of FIG. 4;

FIG. 7 is a fragmentary, elevational view of another embodiment ofmechanism for transmitting rotary motion through the handpiece; and

FIGS. 8, 9 and 10 are fragmentary elevational views, in verticalsection, showing the cup-carrying end of the handpiece with differentembodiments of means for releasably retaining the cup on the rotor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The dental prophylaxishandpiece, as seen in FIGS. l-3, comprises an elongated, substantiallycylindrical body member 12, having housing 14 secured to one endthereof, and hollow, cylindrical head 16 at the other end. Head 16 isdisposed transversely to the axis of the body member, the latterpreferably being offset in the side plane, as shown in FIGS. 2 and 3, inthe same manner and for the same advantageous purposes as set forth inapplicant's earlier mentioned pending application.

Cup 18 is made of flexible material, such as rubber, and is provided forthe purpose of holding a supply of prophylaxis paste and applying it tothe teeth, as in conventional dental instruments of this kind. Rotationis imparted to cup 18 by a rotor within head 16, the rotor in turn beingrotated by flexible cord 20, as explained later in more detail. Cord 20extends essentially axially through body member 12, passing beneathroller 22 to effect the necessary directional change between theangularly offset portions of the body member. Preferably, a pair ofindependently rotatable rollers are provided on a common mounting pinfor the two reaches of the cord extending through the body member. Suchstructure is set forth in detail in the aforementioned copendingapplication, and may be the same in the present invention.

Housing 14 includes inlet 24, for connection to a compressed air supply,and discharge 26 through which air is vented after passing through thehousing to effect rotation of a rotary member therein, an example ofwhich is shown and described later. The rotary member is attached to oneend of shaft 28 which is journaled at the other end in support 30. Adouble helical groove is cut into the periphery of shaft 28 with theends joined so that the groove is endless. Thus, as shaft 28 is rotatedin one direction, a follower riding in the groove and constrained tomove linearly would travel back and forth on the shaft, its directionbeing reversed at each end of the groove. Such mechanism is well knownand has been previously used in other applications, such as line guideson fishing reels.

With particular reference to FIGS. 4, 4a and 5, shaft 28 passes looselythrough an opening in block 32 and cord is secured to the side of theblock by means of post 34, extending integrally from the side of theblock and around which the ends of the cord may be looped, thuseliminating the necessity of a spliced, endless cord. The other side ofcord 20 is also seen in section in FIG. 4, passing along the side ofblock 32, but not in contact therewith. Follower 36 is loosely insertedin an opening in block 32 communicating with the opening through whichshaft 28 passes, and is retained by pivoted key 38. An end portion offollower 36 extends into the double helical groove so that rotation ofshaft 28 is transmitted through follower 36 to cause movement of block32. Both pivoted key 38 and fixed key 40 on block 32 (see FIG. 4a) ridein keyway 42 within body member 12, thereby constraining motion of block32 along a linear path defined by the keyway. Pivoted key 38 serves thedual function of releasably retaining follower 36 within block 32 and ofriding in keyway 42, while fixed key 40 serves only to ride in thekeyway, thereby stabilizing travel of the block.

A pair of small pulleys or rollers 44 are independently supported forrotation about parallel axes on opposite sides of shaft 28 adjacent theend thereof extending from housing 14. Pulley 46 is mounted for rotationabout an axis perpendicular to those of pulleys 44 and parallel to shaft28, as best seen in FIG. 5. Cord 20 passes around both of pulleys 44 andover pulley 46, being constrained at the top by the upper supports forpulleys 44, extending parallel to pulley 46. Thus, the cord is driven bymovement of block 32 and guided at one end of the handpiece by pulleys44 and 46, being maintained out of contact with shaft 28 and passing oneach side of support 30.

FIG. 6 shows diagrammatically a suitable embodiment of rotary member formovement by the air flow through housing 14. Rotor 48 has radial slotsin which vanes or blades 50 are slidably inserted. The rotor iseccentrically mounted in cavity 52, thus providing greater clearancebetween the rotor and cavity wall on one side than on the other. Thisallows centrifugal force to move the blades outwardly from the surfaceof the rotor where clearance is sufficient, and the air pressure.radially reciprocating blade rotor is a conventional mechanism, beingcommonly used in pumps where'the rotor is powered and the blades used tomove a liquid.

If air flow is used to power the'moving parts of the handpiece, theon-off control may conveniently comprise a simple valve in the path ofthe pressurized air. In FIGS. 1 and 3, inlet 24 is illustrated partiallyin section to reveal slide valve 54 interposed in inlet 24 and biasedtoward the closed position by spring 56. Extending from a fixedconnection with the valve closure member is slider bar 58, movablysecured to body member 12 by rivets 60, or the like, extending throughelongated slots in the bar. Finger button 62 forms the terminal end ofslider bar 58 and is positioned at a convenient location on the bodymember for engagement by the index finger when the handpiece is beingheld and used in the normal manner. Bar 58 is shaped as required toextend as directly as possible from the valve to the desired locationfor the finger button, two different shapes being shown for theembodiment of FIGS. 1 and 3.

The FIG. 1 embodiment of the handpiece includes a paste dispensingmechanism such as that disclosed in the aforementioned copendingapplication. A paste dispensing cartridge of the type shown therein isinserted in the open, upper side of cylinder 64. Plunger 66 is advancedto force the paste from the cartridge through tube 68 (FIG. 2) extendingfrom the end of cylinder 64 to means communicating with the interior ofcup 18. Construction and operation of this portion of the apparatus maybe identical with that of the prior application, to which reference maybe had for any additional details. The present application, however,will presently describe a combination of the paste dispensing mechanismwith a cup construction which is removable and disposable after each usewithout need of handling the rotor which drives the cup.

In FIG. 7 is shown an embodiment which does not utilize thereciprocating rotation feature, but nevertheless incorporates all movingparts in the handpiece. Housing 14, with air inlet 24 and outlet 26, arethe same as previously described. Shaft 70 carries gear 72 which drivesgear 74. The latter carries a drive wheel around which cord 20 passes infrictional engagement. Again, the cord is wrapped around the rotor whichdrives the cup to impart rotation in the same manner, except in only onedirection. Although elimination of the bevel gears used in prior artprophylaxis handpieces was one of the major advantages of applicantsprior copending application, the addition of such gears in the mannersuggested in FIG. 7 would not sacrifice this advantage since the gearsare not located immediately adjacent the cup and therefore would not besubject to tioned on the handpiece as shown in the prior application,rather than the finger button and slide bar. Conventional means could beprovided for achieving an appropriate rotational speed of the cup inrelation to that of the motor. In the disclosed embodiment, theavailable air pressure would be regulated to provide the normal cupspeed of 600-700 rpm, either directly or an equivalent speed forreciprocating rotation. About 2 /2 to 3 revolutions of the cup in eachdirection are desirable, which may be achieved with a 1% inch travel onthe helical groove within dimensional constraints of a typical sizehandpiece.

Turning now to FIG. 8, details of the cup-carrying end of the handpieceare shown in an embodiment incorporating the paste dispensing mechanismof FIGS. 1 and 2. Rotor 76 is mounted for rotation within hollow head 16and includes integral end flanges 78, having an outside diameter onlyslightly smaller than the inside diameter of head 16, and a centralportion of reduced diameter. Cord is wrapped 1 /2 turns (540) around thecentral portion of rotor 76, the side of head 16 attached to body member12 being open to allow passage of the cord without contact. Rotor 76 ispreferably constructed of low friction plastic, such as Teflon. A holeextends axially through rotor 76 and nipple 80 extends into the upperend thereof. Open end 82 of pastecarrying tube 68 is positioned at theend of nipple 80, and thus within the hole in rotor 76.

Retaining ring 84 is attached to the open end of head 16, as by beingthreaded thereon, and retains the rotor within the head. Cup 18 isfixedly secured, e.g., by cementing or other suitable bonding means, todisc86 from which spindle 88 centrally extends. Cup 18 is assembled torotor 76 by inserting spindle 88 through the open center of retainingring 84 and into the lower end of the hole through rotor 76.Cooperative, resilient attaching means are provided for releasablysecuring spindle 88 to rotor 76, and may take any convenient form. Forexample, the outside dimensions of spindle 88 may normally be slightlylarger than the portion of the hole into which the spindle fits and beresiliently compressed to frictionally retain the cup and rotor inassembled relation. Preferably, a resilient detent retaining means, suchas a protuberance on one member cooperating with a recess in the other,is provided, as shown and described more fully in the FIG. 9 embodiment.Also, the cross-sectional shapes of the lower end of the rotor hole andspindle 88 should be square, or at least non-circular, to insure directtransmission of rotation from the rotor to the cup. The upper end of therotor hole is, of course, circular in cross-section since nipple 80 doesnot rotate.

Spindle 88 includes an axial opening which extends through the spindle,disc 86 and into the adjacent portion of cup 18. Thin wall section 90separates the end of the passageway defined by the openings through therotor, spindle and disc from the apex of the cup concavity. Cuts areprovided in wall section 90in the same manner as described in theaforementioned copending application, wherein three radial cuts in theindicated portion of the cup are provided to allow paste to be forcedinto the concavity of the cup, but preventing reverse flow. That is, asplunger 66 is depressed paste will In FIGS. 9 and 10 are shownembodiments of cooperative rotor and cup detachable mounting means foruse with the handpiece of FIG. 3, i.e., without the paste dispensingunit. Common reference numerals are used for elements which are commonto'the various embodiments. In each case, rotor 76 includes flanges andis r0- tatably mounted within head 16. Cord 20 is wrapped around therotor to transmit rotation thereto in the same manner, and retainingring 84 is secured to the open end of head 16 to maintain the rotortherein.

In the FIG. 9 embodiment, rotor 76 again includes an axial openingextending therethrough, and cup 18 is again bonded to a disc and spindlemember. However, no central opening is provided through the disc andspindle, respectively numbered 92 and 94 in this embodiment, since nopaste is supplied therethrough. Instead, spindle 94 is split for aportion of its length by groove 96, extending from side to side throughthe spindle. Protrusions 98 on the outer surface of the spindle arereceived in similarly shaped recesses in the wall of the opening inrotor 76. The free end of spindle 94 is rendered somewhat resilient bythe provision of groove 96, thereby allowing the end of the spindle tobe compressed as required for manual insertion into and withdrawal fromthe rotor opening. Suitable dimensioning is provided to avoid unduefriction between disc 92 and the opposing surface of retaining ring 84as the disc is rotated.

The FIG. 10 embodiment is perhaps simplest of all since the cup is notrequired to be bonded to another unit, and the rotor does not requireinternal openings. Instead, knob 100 extends from the end of rotor 76,through the open end of head 16 and the central opening of retainingring 84. Cup 18 is formed with recess 102, similar in shape to knob 100for insertion thereon. Since cup 18 is made of rubber, recess 102 may beslightly smaller than knob 100, if desired. The cup will thus befrictionally engaged with the knob and rotation will be imparteddirectly from the rotor to the cup.

It is apparent from the foregoing description that the present inventionprovides a prophylaxis handpiece requiring no moving parts whateverexternally of the handpiece itself. Rotation is imparted to the toothengaging cup without the use of bevel gears immediately adjacent thecup, and reciprocating rotation of the cup may be provided, again bymechanism contained within the handpiece. Embodiments have beendisclosed both with and without delivery of paste directly to the cuprecess from the inside, while in each case the cup may be easily andquickly inserted on and removed from the handpiece without handlingother elements thereof. The individual cups may thus be convenientlyremoved and discarded after use in a single cleaning operation and afresh, sterile cup placed in operative position virtually effortlessly.

Although several embodiments of the invention have been illustrated anddescribed, it is to be understood that the invention is not limitedthereto. As various changes in the construction and arrangement may bemade without departing from the spirit of the invention, as will beapparent to those skilled in the art, reference will be had to theappended claims for a definibe forced from the cartridge through tube68, out of tion of the limits of the invention.

end 82 thereof, through rotor 76, spindle 88, and thence into cup 18through the cuts in wall section 90.

What is claimed is: l. A dental prophylaxis handpiece for polishingteeth by forcibly rubbing thereon an abrasive dentifrice paste with arotary element said handpiece comprising, in combination:

a. a hollow, elongated body member;

b. a rotary tooth engaging element adapted to carry a quantity ofdentrifrice paste and extending from one end of said body member;

0. reciprocating motion means for imparting rotational movement to saidelement and for alternately reversing the direction of rotation of saidelement after several revolutions in each direction; and

d. means for selectively supplying power to said reciprocating motionmeans to effect rotation of said element.

2. The invention according to claim 1 wherein said reciprocating motionmeans comprises a rotary member contained within said handpiece poweredby compressed air supplied to said handpiece through inlet meanstherein.

3. The invention according to claim 1 wherein said reciprocating motionmeans comprises a powered member mounted in said handpiece remote fromsaid element, a cylindrical rotor to which said element is attached forrotation thereby, and a flexible cord driven by said powered member andpassing in contacting relation with said rotor to impart rotationthereto.

4. The invention according to claim 3 wherein said element comprises ahollow cup, the axis of rotation of which is essentially perpendicularto the axis of that portion of said body member from which it extends,and coaxial with said rotor.

5. The invention according to claim 1 wherein said reciprocating motionmeans includes a shaft having an endless, double helical groove andconstrained against other than rotational movement means for impartingrotation to said shaft, a follower riding in said groove, and a flexiblecord attached to said follower for movement therewith and to saidelement to transfer motion from said follower to said element.

6. The invention according to claim 5 wherein said flexible cord istwo-ended, each end being connected to said follower.

7. The invention according to claim 1 wherein said reciprocating motionmeans includes a linearly reciprocating member and a flexible cordhaving two ends, each anchored to said element.

8. The invention according to claim 1 wherein said reciprocating motionmeans includes a powered rotary member, first motion transition meansfor converting rotation of said powered member to reciprocating linearmotion, and second motion transition means for converting saidreciprocating linear motion to reciprocating rotational motion of saidtooth engaging element.

9. A dental prophylaxis handpiece for polishing teeth by forciblyrubbing thereon an abrasive dentifrice paste with a rotary element saidhandpiece comprising, in combination:

a. a hollow, elongated body member;

b. a rotary tooth engaging element extending from one end of said bodymember;

c. a powered member mounted in said handpiece remote from said toothengaging element;

(1. a cylindrical rotor to which said element is attached for rotationthereby; and

e. a flexible cord driven by said powered member and passing around, incontacting relation with, said rotor for more than one complete 360turn, whereby an extended contact area between said cord and rotor isprovided to insure non-slip transmission of motion.

10. The invention according to claim 9 wherein said rotor and cupinclude cooperative structure for releasably maintaining said cup inoperative engagement with said rotor, said structure allowing attachmentand detachment by manual engagement only of said cup.

11. The invention according to claim 10 wherein said cooperativestructure includes a protrusion on one of said rotor and cup, and arecess in the other for resilient deformation to receive saidprotrusions and maintain said rotor and cup in frictional engagement.

12. The invention according to'claim 10 wherein said cooperativestructure includes a spindle extending from said cup for insertion in ahollow central portion of said rotor, and resilient detent means formaintaining said releasable engagement.

13. The invention according to claim 10 and further including means onsaid body member for receiving a supply of cleaning paste, and conduitmeans for conducting the paste from said supply into the hollow of saidcup in response to selective manual displacement of the paste withinsaid supply.

14. A dental prophylaxis handpiece for polishing teeth by forciblyrubbing thereon an abrasive dentifrice paste with a rotary element saidhandpiece comprising, in combination:

a. a hollow, elongated body member;

b. a hollow cup adapted to carry a quantity of dentifrice paste andextending from one end of said body member;

c. first means for imparting rotational movement to said tooth engagingelement;

d. second means for selectively supplying power to said first means toeffect rotation of said element;

6. third means on said body member for receiving a supply of cleaningpaste; and f. conduit means for conducting paste from said third meansinto the hollow of said cup in response to selective manual displacementof said third means. 15. The invention according to claim 14 whereinsaid third means comprise a plunger having a first end engaging saidpaste supply and a second end positioned for manual engagement toadvance said plunger, and thereby said paste.

16. The invention according to claim 15 and further including detentmeans cooperable with said plunger to control manual advancementthereof.

1. A dental prophylaxis handpiece for polishing teeth by forciblyrubbing thereon an abrasive dentifrice paste with a rotary element saidhandpiece comprising, in combination: a. a hollow, elongated bodymember; b. a rotary tooth engaging element adapted to carry a quantityof dentrifrice paste and extending from one end of said body member; c.reciprocating motion means for imparting rotational movement to saidelement and for alternately reversing the direction of rotation of saidelement after several revolutions in each direction; and d. means forselectively supplying power to said reciprocating motion means to effectrotation of said element.
 2. The invention according to claim 1 whereinsaid reciprocating motion means comprises a rotary member containedwithin said handpiece powered by compressed air supplied to saidhandpiece through inlet means therein.
 3. The invention according toclaim 1 wherein said reciprocating motion means comprises a poweredmember mounted in said handpiece remote from said element, a cylindricalrotor to which said element is attached for rotation thereby, and aflexible cord driven by said powered member and passing in contactingrelation with said rotor to impart rotation thereto.
 4. The inventionaccording to claim 3 wherein said element comprises a hollow cup, theaxis of rotation of which is essentially perpendicular to the axis ofthat portion of said body member from which it extends, and coaxial withsaid rotor.
 5. The invention according to claim 1 wherein saidreciprocating motion means includes a shaft having an endless, doublehelical groove and constrained against other than rotational movementmeans for imparting rotation to said shaft, a follower riding in saidgroove, and a flexible cord attached to said follower for movementtherewith and to said element to transfer motion from said follower tosaid element.
 6. The invention according to claim 5 wherein saidflexible cord is two-ended, each end being connected to said follower.7. The invention according to claim 1 wherein said reciprocating motionmeans includes a linearly reciprocating member and a flexible cordhavinG two ends, each anchored to said element.
 8. The inventionaccording to claim 1 wherein said reciprocating motion means includes apowered rotary member, first motion transition means for convertingrotation of said powered member to reciprocating linear motion, andsecond motion transition means for converting said reciprocating linearmotion to reciprocating rotational motion of said tooth engagingelement.
 9. A dental prophylaxis handpiece for polishing teeth byforcibly rubbing thereon an abrasive dentifrice paste with a rotaryelement said handpiece comprising, in combination: a. a hollow,elongated body member; b. a rotary tooth engaging element extending fromone end of said body member; c. a powered member mounted in saidhandpiece remote from said tooth engaging element; d. a cylindricalrotor to which said element is attached for rotation thereby; and e. aflexible cord driven by said powered member and passing around, incontacting relation with, said rotor for more than one complete 360*turn, whereby an extended contact area between said cord and rotor isprovided to insure non-slip transmission of motion.
 10. The inventionaccording to claim 9 wherein said rotor and cup include cooperativestructure for releasably maintaining said cup in operative engagementwith said rotor, said structure allowing attachment and detachment bymanual engagement only of said cup.
 11. The invention according to claim10 wherein said cooperative structure includes a protrusion on one ofsaid rotor and cup, and a recess in the other for resilient deformationto receive said protrusions and maintain said rotor and cup infrictional engagement.
 12. The invention according to claim 10 whereinsaid cooperative structure includes a spindle extending from said cupfor insertion in a hollow central portion of said rotor, and resilientdetent means for maintaining said releasable engagement.
 13. Theinvention according to claim 10 and further including means on said bodymember for receiving a supply of cleaning paste, and conduit means forconducting the paste from said supply into the hollow of said cup inresponse to selective manual displacement of the paste within saidsupply.
 14. A dental prophylaxis handpiece for polishing teeth byforcibly rubbing thereon an abrasive dentifrice paste with a rotaryelement said handpiece comprising, in combination: a. a hollow,elongated body member; b. a hollow cup adapted to carry a quantity ofdentifrice paste and extending from one end of said body member; c.first means for imparting rotational movement to said tooth engagingelement; d. second means for selectively supplying power to said firstmeans to effect rotation of said element; e. third means on said bodymember for receiving a supply of cleaning paste; and f. conduit meansfor conducting paste from said third means into the hollow of said cupin response to selective manual displacement of said third means. 15.The invention according to claim 14 wherein said third means comprise aplunger having a first end engaging said paste supply and a second endpositioned for manual engagement to advance said plunger, and therebysaid paste.
 16. The invention according to claim 15 and furtherincluding detent means cooperable with said plunger to control manualadvancement thereof.